Drain tubing?

Any Idea’s what this tubing installed on drain line is for?

Is it hooked up on both ends at the drain?

Could have been for an old Reverse Osmosis system if only one end is hooked up usually with a saddle valve/ drain saddle.

It is hooked up above the T and what appears to be taped to the bottom of the right side drain line, unable to tell if it has penetrated the drain line or just tapped to the bottom.